Poor sleep is an epidemic in the modern world. Sleep-onset insomnia—the inability to even get to sleep—is pervasive. Shallow sleep and frequent late-night awakenings are common, limiting access to arguably the most important stage of sleep called Slow-Wave Sleep, formerly defined as stages 3 and 4 of the sleep cycle. It is during this stage that memories are encoded from short term to long term, toxins such as beta-amyloids (linked to Alzheimer's) are flushed out, and is when chemicals like adenosine are flushed out, which is needed to feel fully rested and energetic the next day. Slow-Wave Sleep is characterized by very slow electrical brain wave oscillations from 0.1 hz to as high as 3 hz. It is the deepest stage of sleep and the hardest to reach.
One problem is that in even in the deepest stages of sleep, the brain is monitoring the audio of its surroundings intently for potential signs of danger. Unfortunately in the modern world this becomes a challenge to achieving healthy sleep, as the noises of everyday life have increased dramatically, even as the level of danger has decreased. This has led to problems getting to sleep, staying asleep, and in reaching that critical Slow-Wave Sleep Stage.
Previous inventions have used white noise to mask unwanted sounds, as shown by U.S. Pat. Nos. 9,694,154 and 8,019,092. However, white noise has been shown in laboratory experiments to be detrimental in some cases, as a more enriched sound environment supports healthy brain growth, even during sleep. White noise is often used as a control in sleep research because it is ineffective at truly enhancing sleep. Similarly, nature sounds like rain have been used, as shown by U.S. Pat. No. 7,749,155. But again, these sounds are often very white-noise-like and serve only to mask outside sound. In fact, some systems have endeavored to mask sounds entirely, as shown by U.S. Pat. No. 9,613,610. Still the problem remains—merely masking sound does not promote or enhance sleep. The fact is, if white noise, nature sounds, or any type of sound muffling or masking worked to alleviate the problem of insomnia, it would have done so a century ago.
Other previous inventions have attempted to use biofeedback devices to monitor sleep and present pleasant sounds, masking sounds, white noise, and other audio based on EEG or other physiological data, as shown by U.S. Pat. No. 7,041,049, U.S. Pat. App. Nos. 2013/338429, 2016/151602, and 2015/258301. Some have even targeted slow-wave sleep itself, as shown by U.S. Pat. App. No. 2017/304587. All of these inventions require the use of biofeedback of EEG devices, which are expensive, hard to manufacture, extremely invasive, and notoriously unreliable as consumer units. Furthermore, most suffer from much the same fundamental problems of other sound masking systems in that they use white noise or other masks.
Other large devices such as those that deliver vibro-acoustic therapies as shown by U.S. Pat. App. No. 2010/179458, have additional limitations as well as the same invasiveness and large expense as biofeedback machines.
Other previous inventions have attempted to use traditional lullabies or other spoken-word methods like hypnosis, as shown by U.S. Pat. No. 9,415,184. While these may work for some people, for most adults they would be annoying and would only work for sleep-onset and not act to enhance sleep throughout the rest of the night.
Finally, previous inventions have endeavored to affect the electrical activity of the brain directly, this activity being called brain waves. One such method is call binaural beats, as shown by U.S. Pat. App. No. 2014/343354. However, binaural beats have been proven ineffective through scientific research. Binaural beats require frequencies in either ear that are inherently off-key, creating a stimulus that is boring, unchanging, or subliminal Other systems have used modulation of pleasing sounds as shown in U.S. Pat. No. 3,884,218, but rely on an EEG wave shape or target the wrong brain waves frequencies entirely as in U.S. Pat. No. 3,712,292. These systems also suffer from a lack of variance—they make only one kind of sound during the night. This is not only annoying and repetitive, but is also subject to what is called habituation, where the brain pays less and less attention to sounds that are always present, until they register barely any brain wave impression at all. There are other effective methods of affecting brain waves as shown in U.S. Pat. No. 7,674,224, but without salience, variance, and modulation patterns specifically adapted to sleep, these methods will not be effective.